EFFECT OF ANTIIMMUNOGLOBULIN ANTIBODIES PRODUCED IN CATTLE INFECTED WITH TRYPANOSOMA-EVANSI ON ANTIGEN-DETECTION ELISA

The possibility of interference with the antigen-detection ELISA for t rypanosomosis by anti-rodent IgG antibodies produced in cattle infecte d with Trypanosoma evansi was investigated. Two different ELISA for de tection of trypanosome antigen and three different systems for anti-ro dent IgG antibody detection were established. The former two were resp ectively polyclonal antibody-based and a combination of monoclonal and polyclonal antibody-based assays. The latter three were also adapted for detection of anti-mouse IgG, anti-rabbit IgG and anti-IgG antibodi es cross-reactive with both rabbit and mouse IgGs. A total of 170 samp les were collected from a dairy cattle farm where an outbreak of T. ev ansi infection was reported. One hundred and two cattle (59%) were fou nd to be positive for trypanosome antigens by the polyclonal antibody- based assay and 86 (51%) were positive by the combination-based system . On the other hand, 51 (30%) and 10 (6%) of cattle had anti-rabbit an d anti-mouse IgG antibodies respectively but none had antibodies cross -reactive with both IgGs. Of the 102 cattle positive for trypanosome a ntigens in the polyclonal antibody-based ELISA, 48 (47%) were also ant i-rabbit IgG antibody positive. It is concluded that antigen detection ELISA based on a single-species immunoglobulin for capture and detect ion might misdiagnose T. evansi infection. Results indicate that this bias will be avoided if reagents for capture and detection are derived from different species. (C) 1998 Australian Society for Parasitology. Published by Elsevier Science Ltd. All rights reserved.